Old Work Permit - Supplementary Work, Timeframe to leave?

I am currently on the old Work Permit scheme, and am currently thinking of resigning - possibly go travelling before returning to my home country.

I have a couple of questions in relation to this:

1. If I submit a resignation, and am placed on 'gardening' leave, am I still allowed to take up supplementary work (i.e. freelance) during this period? This is to get as much money as possible for travelling.

2. After my last official day with my company, how long do I have before I have to leave the country? After the day that I have to leave the country, can I leave to go travel in Europe, for example, and return to the UK again to travel a bit more before I leave for good?

Thanks in advance!