To acquire an unlimited company, both parties only need to agree on terms and prices, and then go through the formalities of renaming at the commercial registration authority and notify the tax bureau. If you want some protection, you can spend money to find a law firm to open a sales contract and ask a lawyer to witness the transaction.
Limited company depends on whether it is a listed company. If so, it must comply with the acquisition regulations of the CSRC and be carried out by professionals.
If not, it would be much easier. As long as both parties agree on terms and prices, all shareholders of the other party agree. Then find an accountant to audit the company's accounts and find a law firm to make a sales contract. After the transaction is completed, go to the commercial registration office to change the name and notify the tax bureau.