is there a way to focus on a specific tab in chrome (via plugin)

You can also use https://developer.chrome.com/extensions/tabs#method-highlight

chrome.tabs.get(tabId, function(tab) {
  chrome.tabs.highlight({'tabs': tab.index}, function() {});
});

You should be able to do this with chrome.tabs.update.

var updateProperties = { 'active': true };
chrome.tabs.update(tabId, updateProperties, (tab) => { });