Firstly: Slight Movement Out of Need
It is permissible to move slightly  The criterion for what makes a slight movement in prayer returns to customarily acknowledged practice according to Shafi`is and Hanbalis. The most correct opinion according to Hanafis regarding the difference between a slight movement and a lot of movement is if a person were to observe him from afar and not doubt that he is not praying, then it is a lot of movement and invalidates the prayer. If the observer remains doubtful, the prayer is not invalidated. Malikis provide the following examples of slight movements in prayer: blinking, scratching the body, gesturing with the hand, and walking to close a nearby gap in the line of prayer. out of need in prayer, and this does not invalidate it. Consensus on this was related by Ibn Rushd, Ibn `Abd al-Barr, and al-Zayla`i.
Secondly: One Praying Responds to Salams with a Hand Gesture
One praying responds to salams with a hand gesture. This is the position of the majority: the Malikis,  The strongest opinion among Malikis is that it is wajib to respond to salams with a hand gesture when praying. Shafi`is,  The Shafi`i position is that it is mustahabb to respond to salams immediately with a hand gesture, or after the prayer in words. and Hanbalis. Most scholars are of this view.
Thirdly: Spitting in Prayer
It is generally permissible to spit in prayer if there is a need. Ibn Battal related consensus on this.
Fourthly: Praying in Sandals
It is permissible to pray in sandals  However, if mosques are carpeted and clean and one fears making them dirty, or fears pushing people away, he should not pray in them. if they are known to be pure.  The sandals should be wiped of dirt and anything unpleasant if one intends to pray in them. This is true in general.  There is a difference of opinion regarding praying in sandals inside the Ka`bah. Ibn Taymiyyah and Ibn Rajab related consensus on this.
Fifthly: Killing Scorpions and Poisonous Snakes in Prayer
It is permissible to kill scorpions and poisonous snakes in prayer. This is the position of the majority: the Hanafis, Shafi`is, Hanbalis, and one position among Malikis. It is also the position of the majority of scholars.
Sixthly: Smiling in Prayer
Smiling in prayer does not invalidate it. This is by agreement of the four schools of jurisprudence, and is the position of the majority of scholars.
Seventhly: Prostrating on the Round Part of a Turban
It is permissible to prostrate on the round part of a turban, but it is makruh without a valid reason. This is the position of the majority: Hanafis, Malikis, and Hanbalis. It is also the position of some of the Salaf.
Eighthly: Using a Legislated Invocation for Something Outside of Prayer
Prayer is not invalidated by glorification or supplications if it does not address a created being, such as when one: sneezes and praises Allah, sees something that disturbs him and says: “Truly, we belong to Allah, and unto Him we return”, or sees something that amazes him and says, “Glorified be Allah”. This is by agreement of the four schools of jurisprudence.  Hanafis make it a condition that one intends not to respond to anyone else.