Citizenship- Is divorce certificate mandatory to prove that I'm separated

Hi there,
I'm applying for my british citizenship - ILR route holding an Indian passport.
I have been seperated for 3 years and divorce petition was filed in India 2 year ago. Due to lockdown's and current situation my divorce proceedings have been delayed and might take another year to reach a final decision.

I would like to know if the home office would accept a document from my lawyer stating the divorce petition has been filed to prove I've been separated or do I have to wait till my divorce is granted and then apply with the certificate.

The application also requires information on the actual end date of the marriage - I'm not quite sure if this is the date we got separated or date I filed a divorce or date I was granted a divorce ?
1) Date your previous marriage or civil partnership ended
2) Reason your previous marriage or civil partnership ended

Thanks for your help in advance

You are not officially divorced until the court grants the final decree stating the divorce is granted or in effect . Until then you are still married.

Evidence of divorce is Not required for citizenship.

Thank a lot for your reply. I agree until divorce is granted I'm married, but not sure why it wouldn't be separated. I have been separated from my ex-partner for more than 3 years. I'm unsure if I said as "married" I would have to provide my partner's details - which I'm not is a position to provide.

The options available on the online application for relationship status are as follows:
1) Single
2) married or civil partnership
2) Unmarried partnership
3) divorced
4) separated
5) widowed

Additionally, if I selected "separated" the application asks for a "date of separation" and "reason for separation". Is this the date moved in separately or the date I applied for my divorce. Would I need to give any proof of document to support my relationship status. Any guidance on this matter is really appreciated.

Thanks for your support.

There is no requirement to supply proof of your relationship status unless you apply as spouse of a British citizen.
However, in the UK a separation can be "legalised". But I believe if you don't have a "legal separation" you are still married.
See the link: https://www.gov.uk/legal-separation