Probably discussed before...couldn't find it....

When is it appropriate for you to discuss what you want?

I would assume after verification but not via phone or email......

When you first meet up or after the play starts?

or just your average play date menu items.

if you have done your research properly, you should have a good idea of what activities she is willing to participate in.  If you want something that does not appear to be on her menu, you really can't discuss it ahead of the date, unless you want her to terminate your discussion.  Quality providers will not discuss what activities they will do over the phone or in texts or emails.  So unfortunately, you will have to wait until you are alone with her behind closed doors.  It kinda sucks, but that's the way the hobby works.

Swim

If you read all the reviews of the provider your interested in, you will get a very good idea of whats on offer.

Do the providers know about these reviews?  I mean can they read them?

1. they know about them &
2. they have paid for full VIP or they have the free limited provider VIP (which allows them to read only their own reviews.)
otherwise no they can not read them though they may know about them.

It is true that some providers don't know about TER and may not know they have reviews on this site.