Your first option is to visit as a tourist. This allows you to stay in the entire Schengen zone, including Portugal, for 90 days in any rolling 180-day period. That could be 90 days straight in a ...
Portugal, Slovakia, Slovenia, Spain, Sweden and Switzerland have all acceded to the Schengen Agreement and are thus Schengen states. Holders of Schengen visas (text on the visa reads “valid for ...