@nivethaS
If your goal is redirection from /page1.html to /page1-alias.html, then you should use the Rewrite Rule directive:
RewriteRule /page1.html /page1-alias.html [R=301,L] - for 301 redirect (the path shown in browser will be /page1-alias.html) or
RewriteRule /page1.html /page1-alias.html [PT] (the path shown in browser will be /page1.html)
https://httpd.apache.org/docs/2.4/mod/mod_rewrite.html#rewriterule
https://httpd.apache.org/docs/2.4/rewrite/flags.html