I have a 2010 A3 TDI s line and i am looking for a set of the 18" Audi tt wheels and i am confused on a few things

1. what model is my car (B5, B6, B4)??? WILL OTHER WHEELS FIT THAT ARE ANOTHER # ??

2. can anyone tell me what the largest suggested wheel will fit well. i have read a 18" is good

3. pretty sure i am looking for 5 x 112 38-45ish on the offset????

thanks in advance and excuse my ignorance- also let me know if you have these 10 spoke TT wheels for sale