Yes... and longer.... and usually, yes you can ( but slower) and no... we don't lose fitness that quickly!
The exercise you do on rest days all helps the fitness, so if injured, that is useful... and unless the injury is particularly serious, e.g. After a calf tear, I did have to move back slowly over a period of weeks, but that was really about muscle healing time and not fitness levels. I exercised every day...( not that leg) whilst on the IC :)...
.....you should be able to pick up where you left off. A brisk walk or a little jogette will let you know how you body is coping. Folk sometimes go back a run, just to check themselves out or for confidence reasons Hope this helps.
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