You can embed a spreadsheet so that no pop-out icon shows.
<iframe height="500" src="https://docs.google.com/spreadsheets/d/SPREADSHEET ID/edit?usp=sharing&embedded=true&rm=demo" width="75%"></iframe>
Use the code section of the Embed function to insert your iframe code.
With this method the frozen rows stay frozen when the viewer scrolls the sheet.
A side effect of this method is that the page automatically scrolls down to the document area.
Idea posted by ChiefChippy2 here
You can have more than one row frozen.
On your computer, open a spreadsheet in Google Sheets.
Select a row or column you want to freeze or unfreeze.
At the top, click View Freeze.
Select how many rows or columns to freeze.