Change back VO2 from Cycling to Running

Get a new running vo2max. Newest of both is used. 

Sorry don't understand what you mean 

The watch keeps track of several VO2 Max values, and uses one for the "main" value used for display in widgets, fitness age, etc. The one that is selected is based on priorities. The top priority is for running, then cycling, walking and last is "all-day heart rate". 

If you don't have a running activity producing a new VO2 Max for a while, the watch switches from running to cycling VO2 Max and vice versa. After 30 days of no activity producing any VO2 Max, the watch will select the walking VO2 Max or maybe the "all-day heart rate" if no walking activity happened.