I gave my kids as much as they wanted. None of my kids really liked it much and they each would become fussy very quickly

I would suggest asking the doctor or a maternal health nurse.

I think this is very much based on each individual child. Tummy time is something that I encouraged with both of my children and the more that you can get them to do it the better. My last little one didn’t like it as much as his sister and as a result learned to roll very quickly. So quickly that the child health nurses thought that it was just a fluke, but he kept on doing it.
I think it’s something that you just need to monitor. If your child is becoming distressed by it then move them onto their back, if they are content then leave them to play. It can also be a great bonding time for parents and babies as you can pull out some favourite toys and encourage play and interaction making tummy time fun.
Tummy time is very important and I would probably say that at least 15 minutes per day would be something to aim for even if you have to gradually get your little one used to it.

Some babies hate tummy time. We forget that floors are hard. If your baby screams, try putting on a soft surface, perhaps a padded playmat the middle of your bed or on a sofa. A friend of mine put her 7 week old baby on her tummy to dry her back after a bath. Bubs rolled herself over onto her back. The Mum was so shocked she rang me up and told me.

I used to give my Bub 15-30mins of tummy time twice a day. I think it is more than plenty.

Start with a couple of minutes a day. Once bugs is comfortable then you can increase it.

this depends on the baby. You really should talk to your doctor about it. Some recommend starting early, others to start later.