1. Depends if the fins are important or not. If they were, I jar before they get aggressive - between 2-3 months. But most often I jar when they become aggressive, usually after 4 months.
2. My tanks are not heated, but I do float them in the fry tank just to get them used to smaller containers. This can also work to acclimate from heated and filtered tanks.
3. Yes but it's safer to do daily specially If you over feed like me or use pellets and or wormy foods.
If they're hurting other fry, jar them. The smaller fry may become stressed and die so it's better safe than sorry.