I am not formally qualified to answer these, but I guess Jewish descent is close enough.
In both cases, the answers are yes. However, actively practising another religion lapses the Jewishness of any Jew - and this has consequences for being able to migrate to Israel as well - though by dropping that, one can become viewed as a Jew again - whether a convert or a born Jew.
However, Reform Judaism views Judaism as purely a religion and ceasing to practise Judaism renders you a Non-Jew, whereas Orthodox Judaism views conversion to Judaism as becoming part of the Jewish ethnicity and thus permanent - though being Muslim or Christian renders your Jewishness dormant until you quit. However, Israel formally only Orthodox Judaism. When a religion isn't recognised in Israel, it doesn't mean it is persecuted but rather, is akin to being formally non-religious: You can migrate to Israel if you are Reform Jewish religiously and Jewish ethnically, but converts to Reform Judaism cannot, whereas converts to Orthodox Judaism can migrate to Israel as Jews, even if they become atheist, for example.
Generally, if you are of Jewish descent and want to be viewed as Jewish, it is better to be an atheist or a member of a religion that is not recognised in Israel, than being member of a religion that is recognised in Israel (other than Orthodox Judaism), such as Christianity or Islam.