Here is a lovely video made by Saffron to explain it all! Cauldron (Potions HUD)
No, if it’s not in your HUD inventory, you ICly don’t have it and must RP accordingly.
To harvest an ingredient you first need to find it, then roll to identify. The item/area will light up once it is correctly identified. You then click the item/area in-world and roll to care for the ingredient to move into your inventory
Because not all ingredients are found in the UK. In fact the climate in the UK can be diverse enough that, for example, plants that thrive in the south of England will simply die in the west of Scotland.
There are a lot of plants that look very similar to other plants which is why not all plants have a lower ID level than a care level. If there are plants in a herbology class that are a high ID level, the professor will roll to identify so you can care for them (pluck the ingredient)!
Unfortunately whether your character would be able to correctly identify a certain plant is determined by your herbology skill level in the HUD. They may know about the plant, but couldn’t correctly identify it out of a lineup of similar plants for example.
Yes, but, do not attach more than one potion HUD at a time or it may cause the potion HUDs to not function properly. When you detach a potion HUD it remains in the state you left it; if you began a brew timer the timer will advance even if the potion HUD is detached.
Taking the potion HUD back into your HUD’s inventory by means of the little triangles icon will not work whilst a potion is brewing. You can, however, detach the potion HUD by means of the little X icon. The HUD will then remain in your SL inventory and, as explained above, the brew timer will continue to advance. We recommend having a special folder in which to store your potions HUDs in order to keep track of them if you plan to do this often.
As far as the HUD is concerned, this isn’t possible. OOCly the player will always know what a potion is or if they have been given one, though your RP may dictate otherwise. It will be on all players to play along appropriately and any problems or disputes which cannot be settled should be brought to the mod team.

Unfortunately Second Life is fickle and objects sometimes happen to disappear with no hope of recovery. If you were about to use a potion and you lose it, please use the form on the HUD status page on the website to report the problem. Admin will investigate and will hopefully be able to resolve the issue. However, please take into consideration the value of the potion lost when requesting a recovery. We understand that brewing potions is work and it sucks to lose one, but investigating issues is work for OOC staff as well. If the potion can be easily re-obtained through other means please seek that method first before contacting staff. Maybe even ICly play it off that the bottle rolled off the table and broke or something.

IMPORTANT - Potions should NEVER be detached from your avatar the usual way, this will result in the potion disappearing. ALWAYS click the potion and select “take” to take it back to your HUD inventory if the bottle has more uses left. You should also never log off while a potion is still attached to your avatar as this will result in the potion disappearing as well.

Each time you drink a potion, an invisible “effect cube” automatically attaches itself to your head, which supplies the text and potentially other effects. If you drink multiple potions, multiple cubes will attach, resulting in multiple lines (and potentially multiple effects). There is an SL limit of attachments (38) so the cubes will attach until that limit is reached. If the text overlaps, you may right click and edit the cube, then drag it up or down slightly. As an aside, we would suggest not drinking multiple potions at once as they can lead to negative in-roleplay side effects including but not limited to: illness, poisoning, the potions not working properly, exploding and death.
Open your Appearance window (in Firestorm the icon looks like a shirt), click on “wearing”, then scroll down to “temporary attachments” and remove any objects in that list.
Your HUD will remain in the state where you left off. If you start a brew timer, it will advance even if you are offline or detach the HUD.
Yes, when taken back to HUD inventory the cauldrons will leave a "dead" version in your SL inventory. Unlike potions they do not attach to a temporary attachment point so that it is possible to detach them during brewing. You may delete the "dead" version from your SL inventory.
Effect cubes attach to a temporary attachment point on your avatar, meaning they will have disappeared when you log back in. If your character would still be under the effect of a potion, please RP accordingly and you may change your regular HUD titler.
Yes. Each cauldron has a different level of durability when you buy them. The more durable a cauldron is, the more expensive it will be. A cauldron loses 2 points of durability from successfully completing a potion brew, but loses 5 points if the brew fails. When the cauldron durability is at 0, it will be unusable. You may check your cauldron’s durability by clicking the “?” button on your potion HUD.
The most straightforward option is to simply buy another one in any store that sells them. However you may choose to seek a cauldron repair person to repair it for you for less than what it would cost to replace. Currently only Alice Hawkins in Snitches Get Stitches in Hogsmeade does cauldron repair. Note that she does not repair pewter cauldrons as they are cheaper to replace than repair.
When purchasing an ingredient from a store you must first find the ingredient in your main HUD inventory, click it and select “rez”, then select “transfer” from the menu that comes up.
Part of a healer’s job is making sure their potions inventory is stocked. This may involve either brewing the potions themselves or traveling to Hogsmeade or Diagon to purchase them if necessary. This also means working out a budget to get money from their boss for purchasing potions or ingredients (after all you can’t be expected to spend your own money for your job). Of course, a healer shouldn’t expect to always have to procure ingredients or potions themselves. Potions from class will be donated to the hospital wing (the good potions anyway), and surely some gullible good-natured donors could be bribed or sweet-talked into sourcing ingredients. Potions and ingredients will not be supplied OOCly however. And remember, not having potions occasionally is valid RP.