A few online bingo questions for the pros out there

Im quite new to on-line bingo (around three months) and have yet to have the chance to withdraw any funds.  I have a few questions that maybe all those experienced folk could answer for me:

1. Free Deposits - ok say I get a free 20 pound trial and I win a few lines/ houses and the cash balance is at 40 pound and bonus is at 10 pound what is the best way to use this 20 pound, can I withdraw? do I need to deposit ( and if so will I lose any funds)

2.  Slots/Instants - whats the difference.  I seem to be pulled to the Cleopatra Instant and once again I do have the odd win (if only I could stop at that lol)

3.  What are the best bingo games to play i.e 90 tables or 75 tables.  Is it best to buy max tickets.

I apologies if I sound stupid but I am confused and am losing quite a bit.  If anyone could advise me on the best way to use my money on online bingo would be great.  Hopefully these questions and answers will help all new comers from all those with experience.

thx avril xx