Whoever does not fast some days of Ramadan has to make up those days before the next Ramadan comes. For more, please see the detailed answer.

The Du`a ‘Allahumma laka sumtu was ‘ala rizqika aftartu’ is narrated in an inauthentic Hadith. There is no source for the Du`a ‘Ashhadu an la ilaha ill-Allah astaghfir Allah as’aluka al-jannah wa a’udhu bika min an-nar.’ The reported Du`a when breaking the fast is ‘Dhahaba ath-Thama’u, wa abtallat al-`urooq wa thabata al-ajr insha Allah.’

There is no specific Du`a for Ghusl, but it is desirable to say Bismillah when beginning the Ghusl.

We do not know of any specific Du`a in the Sunnah for protecting a traveller until he returns to his family safe and sound.

1- Unrestricted Takbir (mutlaq) is not limited to a specific time, and it is Sunnah to say it all the time, morning and evening, before prayer and after prayer, at all times. Restricted Takbir (muqayyad) is limited to the time immediately after prayer. 2- It is Sunnah to recite unrestricted takbir during the first ten days of Dhul-Hijjah and all the days of Tashriq, starting from the beginning of the month of Dhul-Hijjah (i.e., from sunset on the last day of Dhul-Qi’dah) until the end of the days of Al-Tashriq, which is when the sun sets on the thirteenth day of Dhul-Hijjah). 3-With regard to restricted takbir, it starts from Fajr on the day of ‘Arafah and lasts until the sun sets on the last day of the days of Tashriq. 4-The scholars have different views on the formulas of Takbir which are explained in the detailed answer.