Can I get somehow all content (possibly in current scope only) with specified TAG(s) ?
I haven't found anything in search syntax, and such thing like
tag:pricing does not return results tagged with tag pricing
In order to use syntax like that you need to ensure that the "tag" property is a Managed Property in your search configuration. If it does not exist, you may first want to create it, map it to corresponding crawled property and perform a full crawl. After these steps are performed, try above syntax in search text box.
I was working with SharePoint 2010 Search a bit, so there's a refiner on tags, it uses the
MappedProperty="ows_MetadataFacetInfo,popularsocialtags" Managed Property, so you should search like
popularsocialtags:pricing instead of
tag:pricing I think :)