Sick pay is unregulated. It is a gift from some employers, and the rules are whatever the employer says.
Sick time is not required by law, so the employer is in complete control unless there is a union agreement.
I am currently off on sick and my employer is proposing different working times. do i have to reply, or accept this proposal
It depends on the terms of your contract
can a employer contact you while you are covered by a sick note
It depends on the employer's sick leave policies.
Depends. What state are you in? Are a Paid Time Off participant or are your vacation, sick and holiday separate?
This depends on the employer. Most government agencies are more friendly, while private corporations are much more stingy with sick and vacation time. I work for a transit agency, under the Texas Department of Transportation, and we get four hours of sick time per every 80 hours of work. Do the math: That's about 104 hour (13 days) per year.
No the employer will have to give you sick leave once a year .
He can for the day that you claimed to be sick.
YES
How many days are you allowed off sick before a medical certificate is required
This is a matter of policy for each employer or negotiation between employer and employee or union, so that there is no generally applicable answer.