ANSWER:
You must disregard any spotting that come before the period. It is not your menstruation until you see the flow of blood and you must not stop praying, fasting and you can have intimacy with your husband during these spotting. You must wash the affected areas, change the underwear and renew your wudu before praying.
If the flow of blood stops at the end of your menses and you see dryness for one day, take your ghusul and pray. The spotting afterwards only invalidates your wudhu but this is not menses as it comes after your purity.
Purity is identified by seeing a white thread like discharge or by experiencing complete dryness. If you saw your purity once the flow of blood has stopped, you may take ghusl and disregard any spotting that comes afterwards as nothing, you must wash the affected areas, change your underwear and renew your wudhu before each prayer.