Firstly, its important to understand that Allah Most High is transcendently different from His whole creation. Thus, human beings experience emotions, and changes of heart and state, and they fluctuate in their feelings, depending on how they are affected by things around them. Allah the Creator of all things then, is utterly unique and is far above being affected and motivated by anything of the such.
Even when words are ascribed to Him in the Qur’an that resemble what humans feel or do, such as love or mercy or anger, what is to be understood is not with what those words literally entail for created beings, but the tangible end results that those words indicate.
For example, “having mercy” with respect to humans is the softening of the heart that inclines one to favor or do well to someone. With respect to Allah Most High, who is far exalted beyond having a heart and feelings like creation, it means the actual act of doing well for one of His creation, or His Will to do so – not any sense of emotional change. [al-Bajuri, Sharh al-Jawhara]
So when Allah says He loves a group of people, it entails His praising them, rewarding them and forgiving them. [al-Baghawi, Tafsir]
When Allah says He doesn’t love a certain type of people (say, those who transgress), this does not directly entail their punishment, rather it means that He does not will for them any good, and the point of the statement is to be understood as a strong reason not to be like those people. [Abu Sa’ud, Tafsir]
Using these definitions, to answer your main questions:
1. Allah’s Mercy comes before His Love. Thus, He shows mercy to all of creation by simply blessing each being with bounties such as existence, life, health, etc. His Love, which is a more particular form of His blessing, is reserved in the Qur’an for the more deserving of His servants, such as those who: believe, show excellence, repent, rely on Him, are just, fear Him and those who struggle against wrongdoing for His sake.
If Allah Most High did not love a servant first, they could never love Him. So if we want Allah to love us, we must show love to Him by doing the things He loves and leaving that which He doesn’t love, and we should know that the fact that we were given the ability to love Him, means He loved us in pre-eternity out of His pure largesse and generosity.
In terms of indifference (neither loving nor hating), this does not apply to Allah Most High. Imam al-Alusi says in his commentary: “And there is no middle station between Divine love and Divine hate with respect to Him, mighty is His affair, and that is in contrast to the love and hate felt by human beings, because there is a middle-ground between the two, which is the absence of the two [which is indifference].” [al-Alusi, Tafsir]
2. and 3. – See definitions above.
May Allah Ta’ala make us amongst those who love Him, and amongst those He loves, and those who stay away from that which He does not love.