Chicks, corn and weaning to the outside world

Hi

My chicks are 31/2 weeks old and are going out in a secure pen in the garden during the day - rain permitting - they come in at night but have now spent 2 nights without the lamp on. When could they go out into a broody coop 24 /7?

Also, how old should they be before I let them have some mixed corn?

Thank you

hi i have 3 and half week old hybrid chicks and have started to think about the next type of food i need, should the growers pellets be medicated or not. is there a good brand to buy or are they much the same.