A: Google Sheets has limits and Google also has limits when using APIs and other services such as formulas and scripts.

Google API usage limits:

20,000 API calls per day
6 mins processing time per hour
90 mins processing time per day
50 mb per call

https://developers.google.com/apps-script/guides/services/quotas

A google user’s quota can be limited based on the combined amount of activity from things such as scripts, addons, and formulas (eg. GOOGLEFINANCE).

Google Sheets limits:

Up to 10 million cells per spreadsheet
40,000 new rows max
18,278 columns max
200 tabs max per spreadsheet
1,000 GoogleFinance formulas max per sheet
50 cross-workbook reference formulas max (eg. ImportRange formulas)
50 functions for external data max (eg. ImportData, ImportHtml, ImportFeed, ImportXml)
50,000 characters maximum string length