Limitations in Similar Opportunities in Salesforce

1. Use the Similar Opportunities related list on the opportunity’s detail page to find Closed/Won opportunities with common information.

2. The criteria used to find similar opportunities is determined by your administrator. The search finds a maximum of 10,000 opportunities with close dates in a three-month period and displays up to 300 of the records that best match the search criteria. The results are ranked by the number of matching fields.

3. Results can be filtered by Close date or by matching fields.

4. To see how a record in the search results is similar to your current deal, hover over the opportunity name. The matching fields are highlighted in the Match Criteria sidebar.

For implementing it, check the below link