4-12 min
Per day
 
     
        
                                        -If you have heavy muscle pain, you should take a rest.  But, you can workout if you have light muscle pain. With or without muscle pain, you can do cardio exercise and stretching.
Check this video.
-Many successful people have been exercising for a year.  If you have been exercising for a year, you will not gain weight again.  Many failing people lose weight temporarily in a short period, but when they stop exercising, they gain weight again. You should workout for a year.
Check this video.
-Of course you can rest.  However, there are many stretching videos that can be done in 5 minutes a day.  Feel free to exercise. 
Check 5 minutes playlist.
-5 minutes or 10 minutes is enough. Of course you can exercise longer than that. It's important to continue doing, there is no need to force it for a long time.
-There is a big difference between not doing a little exercise and doing a little exercise. In many cases, a little exercise can help you lose weight. It does not matter if you do hard and long exercises. But it is not necessary.