Can i use 1 code in the subdomain also?

You can apply it to your subdomain where you have landing pages for your products. Each site, including subdomains, counts as a single license. However, please note that sites start with suffixes such as .local, .test, or .staging .dev, are not counted as licenses. So, if your subdomain follows such patterns, it won't consume an additional license. For example, URLs like http://dev.test.com/ or http://staging.test.com won't count towards your license limit.