Yes, a purchase for XF currently gives access for all supported XF versions, including 2.1.
Templates are an advanced feature, and you will need some comfort working directly with BB-Codes. If you are familiar with creating templates in MediaWiki, it's a similar process, just with BB-Codes instead. The template you linked is essentially a TABLE BB-Code with rows that can be filled using template parameters.
Template parameters are defined in your template like:
{{{name}}}
{{{name|default_value}}}
You can use other special BB-Codes in your template like
Code:
[if="{{{name}}} != condition_a"]
some content
[else /]
some other content
[/if]
You can use templates as follows:
Code:
[template]Title
| name1=value1
| name2=value2
[/template]
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