I am on H1 and applied for a change of status to L2.my question is:
1. From which day my status is considered to be changed?
2. If a get a job and received my receipt number for the change of status can I continue doing job?
3. once I receive my receipt number can I quit working,if I don't want to work?
4.if I leave the country for going overseas would I be needing any of documents proving that I worked in US for the dependent visa stamping(L2)?

1. I think your status will be considered from the day you get your L2 stamped on your passport. You will be on AOS from the time you have applied for COS till that day.

2. You have to get your EAD only after which you can start working. That usually takes up to 90 days as per usual timings.

3. Not sure. This is something which even I am looking for. Please let me know if you come to know.

4. You may not need it, but you cannot claim back your H1 (if its not cancelled by your company) if you leave the country and reenter on L2.

**Not legal advise. Use at your own risk**

BTW, please let me know how many days did it take for your to receive your COS from H1 to L2.