With pups, I just let them do what ever they want and really dont do walking just basic them getting used to a leash.
I dont baby them...if they want to leap, jump, run, walk, and be crazy I let them, I just dont ask them to do anything that involved jumping...but if they want to go up stairs, they all the power to them, i think it is great for confidence. At about 6 months I start little things with them...remembe r most of these molosser breeds are working breeds bred to do things
Zero and Chara in regards to heat, i let them decide but with concrete areas I dont push issues because their feet can burn
Exercise is great for dogs and not enough exercise is given in my opinion for most dogs...being pregnant and on partial bed rest I too am guilty so they are out and about 3 or 4 days a week in regards to socialization and good walks