No. The rule is that the visa you are entering the country with will be your purpose of stay or residence, no change allowed especially as far as work is concerned.

No, you must apply for a residence permit from your home country or HK/Macau visa offices. Doesn't matter what the employer tells you, they will not be able convert your tourism visa into a working visa without your passport exiting China. However renewing your visa with the same employer or transferring your visa to a new employer takes 5 minutes and can be done without leaving the country as long as you have all the required documents.

You will have to get invitaton letter and work permit from employer then apply for work visa,Z, outside of china

what forms do you need to change to a new employer? I thought they stopped doing the working visa in HK and that you had to go apply for it at your home country!!?? Any advice?

yes， but you have to go back to your country again after your company prepare the invitation letter and employment permit , company docs. after you got the z visa, then you have to apply for work permit and resident permit within 30days after your entry coz the z visa is only 30 days valid. 

Yes,you can get the work permit to work in china ,but it will cancled your L tourist visa.

And for working visa need spouse to your company worked in ,then the company will prepare all the documents for you in china ,then you back to your own country or hk to get one month Z visa ,Hold One month Z visa enter into china ,within one month Z visa you will finished work permit in china .